1. Field of the Invention
The present invention generally concerns a portable cord, also known as portable cordage, for temporary deployment that attaches, permissibly among other things, temporary work lamps, or lights, along its length, thus nominally a “temporary work light string”.
The present invention particularly concerns (1) the positioning of lamps, or lights, along the length of a temporary work light string, and (2) the management of electrical circuits within a temporary work light string and within any devices, including lamps or lights, that are electrically connected to such temporary work light string.
2. Background of the Invention
2.1 Portable Cords
The present invention will be seen to involve a portable temporary power cord, or cable, that can physically attach and electrically connect along its length, among other things, work lamps.
According to the entry “Portable Cord” appearing circa 2012 in Wikipedia, the free encyclopedia of the Internet, “[a] portable cord, which is also known as portable cordage or flexible cord, is a cable with multiple conductors used for functions requiring flexibility. The cord can be employed for power in a range of applications, such as operating motors in small and large tools, equipment, power extensions, home appliances and machinery.
“Portable cords may be used in commercial, industrial and residential applications. They work well on job sites where resistance to oil, chemicals and abrasion is vital and also perform well in extreme environments—both the heat and the cold, outside or inside. Additionally, some portable cords can be water-resistant or water submersible. Because of their characteristics, portable cords are commonly used in a range of facilities, such as construction sites, mills, mines, sports complexes, or even marinas.
“Although the construction of a portable cord varies depending on the type, a standard cord has at least two stranded copper conductors. The copper stranding, insulation and jacket directly influence the physical properties of the cord.”
The most preferred cord material of the present invention will be seen to be Type SEOW. Continuing in the Wikipedi entry:
“A variety of portable cords, differing in styles, lengths and thicknesses, exist in the marketplace. Common types include Type SJT, SVT, SEOW, SJ, SJOW, SO and SOW. Each has specific applications associated with it. A portable cord is usually made of thermoset, thermoplastic elastomer, or thermoplastic. Thermoset cords have heavy-duty-grade rubber jackets and are extremely sturdy. Thermoplastic elastomer cords have medium-duty-grade thermoplastic elastomer jackets and perform well in cold conditions. Thermoplastic cords have a light-duty plastic compound jacket and thus work for light-duty use.”
The preferred Type SEOE is a Thermoplastic elastomer (TPE). As explained in the 2000 article “Don't Let Your Portable Cord Tie You Up” appearing on the World Wide Web at the Electrical Construction and Maintenance website, “[t]hese cords have medium-duty-grade thermoplastic elastomer jackets. UL designations for these cords are SEOW-A and SJEOW-A. CSA designations for these cords are STW and SJTW-A.
“TPE compounds are lightweight in comparison to the rubber materials . . . [found] in thermoset cords. Approved for indoor and outdoor use, TPE is a better choice than plastic materials for some commercial outdoor construction in northern regions. It performs well in cold temperatures (−50 degrees Celsius/−58 degrees Fahrenheit). You'll see this type of material in some standard extension cords.
“TPE cords resist water, oil, cuts, chemicals, and acid. They also handle exposure to weather, sunlight, and ozone. You can get these in a flame-retardant version. However, the CSA designation for this type of cord (STW) carries no recognition for oil resistance. The agency marks this cable as a “T” type, thermoplastic: a plastic compound.
“Although manufactured like a thermoset product and able to perform in temperatures up to 105 degrees Celsius/221 degrees Fahrenheit, TPE may not stand up in environments where extreme heat and hot oil are factors. When exposed to such circumstances, the cord may disfigure or melt, making it useless.’
2.2 Limitations of Previous Portable Temporary Power Cords
Previous portable temporary power cords attach lamps in fixed positions along the length of the cord, normally at even spacing after an initial interval from the plug that is typically longer than is the space between lamps. Such a construction is, almost by definition, likely unsuitable in detail for the illumination of the interior spaces, or rooms, of a building which rooms are typically not linear, and which are accessed through doors and windows at which points lamps may be inappropriate for, among other reasons, shining in the eyes of persons passing or looking through such portals.
More troublesome than sub-optimal lamp locations are the quite frequent occurrences during construction when more light is needed at a specific location. This entail moving the whole work light string, and all or most of the lamps along it. Reasons for moving the string include so as to prevent the lamps from becoming buried or enclosed or trapped above equipments, avoidance of suspended ceilings and/or of framing and/or of dry wall, or prevention of capture between walls. The operation of moving an entire light string so as to move and relocate but a single lamp may become labor intensive and may even require the labor of more than one person.
Further, and more seriously, lamps that are located in fixed positions along the length of a temporary power cord most typically cannot be replaced if damaged. The only alternative to discarding the entire work light cord is to cut out a damaged light and splice the cord back together in an improved manner, typically leaving both an undesirable bulge on the cord and dimensional unevenness in the location of lights along the cord. This repair requires materials and time, and is seldom done even by skilled electricians upon their own work light cords.
Finally, existing work light cords are normally connected to but a single electrical circuit, which is normally rated at 20 amperes/This means, as a practical matter, that the largest and longest work light strings are no more than ten 100-watt light bulbs, and 100 feet in length. Moreover, the ability to power additional loads from these work light cords—such as at a receptacle at the end of the cord o by screwing into an Edison socket normally taking an light bulb—is limited. It would be useful if the lengths, current capacities, and/or flexibility (in numbers and in positions of the attachment(s) of electrical loads to a work light cord could be improved.